The present invention relates to a turbocharger that includes a water-cooled turbine housing.
A turbocharger includes a turbine housing and a bearing housing, which are coupled to each other. A rotary shaft is connected to a turbine wheel arranged inside the turbine housing so that the rotary shaft can rotate integrally with the turbine wheel. The rotary shaft is supported by the bearing housing.
In the turbocharger disclosed in Japanese Laid-Open Patent Publication No. 2010-48187, a water passage through which cooling water circulates is provided inside a turbine housing. In turbochargers having this type of water-cooled turbine housing, the turbine housing is cooled through heat exchange performed with cooling water flowing through the water passage and is prevented from being overheated.
During operation of the turbocharger, vibrations occur as a result of the integral rotation of the turbine wheel and the rotary shaft. Such vibrations are transmitted to the bearing housing, which supports the rotary shaft. The vibrations transmitted to the bearing housing are also transmitted through the turbine housing to a downstream-side portion of an exhaust passage joined to the turbine housing and contribute to noise generation.
In addition, in turbochargers including a water-cooled turbine housing, the temperature of the turbine housing is comparatively low, and therefore the rigidity of the turbine housing rises, and the vibration transmissibility is high. Therefore, the vibrations that have been transmitted from the rotary shaft to the bearing housing are liable to be transmitted to the downstream-side portion of the exhaust passage through the turbine housing, and therefore noise is easily generated.